The present invention relates generally to duct assemblies for transporting pressurized fluid in buildings such as ductwork for HVAC systems and, more particularly, to various embodiments of a corner flange connection member for placement into corners defined by channel flanges associated with HVAC and other types of ductwork and the method for attaching such corner flange connection members to the ductwork channel flanges including certain improved high speed fastener connectors.
Duct assemblies used to transport pressurized fluid in buildings such as forced air HVAC systems are conventionally formed in sections and secured together to form longer spans as needed. A duct section is typically formed of sheet metal into a rectangular shape having four sides and vent or seamed corners at the intersections of the sides. A flange extends essentially perpendicularly outward from each side at both ends of the duct section. Duct sections are positioned end-to-end such that the flanges of one duct section align with the flanges of an adjacent duct section and the aligned duct flanges are fastened together to form the overall duct assemblies. The flanges which are formed as part of each duct section are not continuous. Rather, there are gaps at each location on the duct sections where adjacent flanges meet for manufacturing convenience. These typically occur at the four corners of the top and bottom sections of a particular duct section. Corner pieces or corner flange connectors are typically inserted into channels formed in each duct flange such that they span the corner gap at each location on the duct section where adjacent flanges meet. When the duct sections are positioned end-to-end, the corner pieces of one duct section are aligned with corner pieces of the adjacent duct section. Fasteners are then inserted through holes extending through the corner pieces to clamp the duct sections together. Typically, a single bolt with a washer and nut are used to complete the duct flange connector. Frequently, gaskets are placed between aligned duct flanges to achieve an airtight seal and clips or screws are used to hold the aligned flanges together between the corner pieces.
One typical corner flange connector or angle plate is disclosed in U.S. Pat. No. 5,342,100 wherein the angle plate is pressed into duct channel flanges which are formed with return side wall bends at their free ends to hold the angle plate in the duct channel flange when the return side wall bends of the flanges are crimped over such angle plate. This angle plate likewise includes upstanding projections or the equivalent thereof projecting in a common direction and being of a height to hold adjacent plates parallel and spaced apart from each other when stacked one on top of the other thereby preventing nesting and permitting the sliding of single plates off the bottom of a stack of plates for use in an apparatus for automatically installing angle plates at the corners of ductwork. This snap or pressing connection of the corner plate into the duct channel flange does not always produce a completely secure connection, even when crimping is used. Not only does this technique allow the corner plates to become separated from the flanges more easily, it also allows adjacent flanges of the duct assembly to move independently of each other. If the corner plates move independently from the flanges, adjacent flanges of the duct assembly can likewise move independently from each other permitting the duct sections to move with respect to each other thereby allowing fluid or air to leak from between the joints. If these corner plates become loose or actually separate from the flanges, additional time is required to reinsert and fasten the corner pieces in the appropriate duct channel flanges and to reattach the adjacent duct sections. A corner flange connection member which achieves a more robust connection and which is easier to install is desirable.
Another known corner member and method for connecting adjacent duct assemblies is disclosed in U.S. Pat. No. 6,471,256. This corner flange connection member requires no pressing or crimping and utilizes nuts and bolts to complete the connection. The joint is formed by passing standard fasteners through a corner flange connection member associated with one duct section, through integral channel flanges associated with the adjacent duct sections which are arranged in end-to-end relationship to each other, and through a corner flange connection member associated with the other duct section. The act of installing the fasteners tightly pulls together the duct flanges and makes an integral connection between them. The use of machine screws, without nuts, which bite into the material of the duct flange when driven through holes associated with the respective arm portions of the connector member and through pre-formed holes associated with the duct flanges thereby forming a threaded inner connection therebetween is likewise disclosed.
Still further, as likewise disclosed in U.S. Pat. No. 6,472,256, corner plates can also be attached to the duct channel flanges by deforming material of the duct flanges through pre-formed holes associated with the corner plates. In this instance, no screws, nuts or bolts are utilized in the joinder method. Other connector member configurations and methods for attaching adjacent duct sections together are likewise disclosed in U.S. Pat. No. 6,471,256. Although all of these corner members and connection techniques improve the stability and rigidity of connecting adjacent duct sections, an easier, faster, and more efficient method for making such connections as well as use of a corner flange connection member which applies greater clamping force to the duct flanges is desirable. In addition, use of a corner flange connection member, improved fasteners and a method of attaching adjacent duct sections which can accommodate for damage and/or malformation/misalignment occurring to the duct channel flanges during manufacturing, transportation and/or assembly without the need for extensive and expensive corrective measures is likewise desirable.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.